A GIANT waterwheel stretching across the Mersey near Ellesmere Port could generate renewable electricity for the North West.

That's the vision of a new study that identifies the river as one of the top sites for tidal renewable energy in the UK.

Experts say the Mersey estuary's large tidal range of 8-10 metres and unusual shape combine to create powerful tidal currents that could be harnessed to produce power.

The waterwheel is just one option. The largest of the projects being evaluated, a tidal barrage across the river, would generate 700 MW of electricity, enough to power 260,000 homes and save 516,000 tonnes of CO2 per year.

According to the Government's energy White Paper on the country's future energy needs, Meeting the Energy Challenge, released last month, tidal power could make a significant contribution towards meeting the twin challenges of climate change and security of supply.

However, the team behind the Mersey study are keen to emphasise that a full barrage is just one of the innovative options being looked at.

Much more likely option are water-wheels, tidal turbines and open stream energy converters. The report describes how the various technologies could be used along the river.

An artificial tidal lagoon could be created in the open sea beyond the mouth of the river, with the flow of water in an out used to generate power.

A tidal fence would comprise vertical turbines housed in submerged cells built across the estuary.

The restriction to the flow created by the fence would accelerate water through the turbines to create power.

A tidal gate could be specifically designed for the shallow waters of the Mersey. The bottom part of the sluice would be fitted with a matrix of compact turbines.

Finally, central reservation in the river could be created to hold a series of open stream turbines.

Professor Peter Guthrie, professor of engineering for Sustainable Development at Cambridge University, has been part of the study team led by consultants Buro Happold.

Professor Guthrie said: 'We have been searching for a way to generate renewable energy on the river that would bring jobs and investment but we must also respect the Mersey estuary's international importance for wildlife.'

The study was co-sponsored by Peel Holdings, owner of the Peel Ports and Ellesmere Port docks, and the Northwest Regional Development Agency (NWDA).

John Whittaker, chair of Peel Holdings, said: 'This is an important step along the way to developing a realistic proposal which can gather public support and government backing.'

Many of the technologies being evaluated are so new they are still under development. For this reason, the experts are likely to recommend a pilot project that would allow testing before full implementation.